i (23F) had a discussion (not argument) with my bf (M25) who i have been with since 2019 about his step sister. So his dad had a mistress during his marriage with his mom (he passed away) and had a daughter born the same year as my bf with another woman. When we began dating she followed me on twitter and i stalked her page lol and saw she made a tweet when they were teens (17 ish) saying my bf was cute. I thought this was odd bc they’re technically siblings but let it go.
Sometimes me and my bf would hangout and she’d call him or text him to talk about her problems with her bf or to ask him to pick her up bc she was “drunk” from places she’d been out with friends.
Recently i noticed he always likes her stories when she posts pictures of herself, he also has 4 other sisters on instagram that are not step sisters and he never liked their stories when they post a selfie etc.
This is when i thought it was odd. I asked him about it and he said “she’s my sister so what” he then got VERY angry and started raising his voice saying “bro why are u even asking this wtf what are you trying to say? wtf you’re weird for that” I didn’t come at him or anything he just got angry and defensive and hung up on me.
Now what I’m wondering is am i wrong for thinking of this as odd? Or off putting? I know some people don’t care about step siblings and don’t see them as that but he said I’m weird and it’s his sister.
I need advice I don’t know if he’s defensive for the wrong reasons or if I’m overthinking.?
TLDR; suspicious of bf and his step sister being romantically involved in the past